1. Field of the Invention
This invention relates to a processing method for brake rotor-equipped wheel bearing devices, and more particularly it relates to a method for cutting the pad slide surfaces of a brake rotor.
2. Brief Description of the Prior Art
Wheel bearing devices for automobiles are used for driving wheels and non-driving wheels. At any rate, in wheel bearing devices, the surface runout of the brake surfaces, i.e., the pad slide surfaces, during rotation of the brake rotor, becomes a cause of brake shudder during braking, so that high processing accuracy and high dimensional accuracy are required of the parts of the wheel bearing device. Even if the processing accuracy is increased, however, not only does the processing errors on the parts accumulate during assembly of the wheel bearing device, but also assembling errors are produced, thus making it impossible to suppress the surface runout of the pad slide surfaces of the brake rotor.
To eliminate such drawbacks, there has already been proposed a cutting method (U.S. Pat. No. 6,247,219) wherein a brake rotor-equipped wheel bearing device, assembled in a mounted state, is mounted on a cutting machine and, with the brake rotor-equipped wheel bearing device supported in a mounted state, the pad slide surfaces are cut while rotating the brake rotor.
According to the above-mentioned conventional method, since the pad slide surfaces of the brake rotor are cut with the brake rotor-equipped wheel bearing device put in a mounted state, the accumulated errors produced by the accumulation of the processing errors of the parts, the strains produced during fixing of the brake rotor, and the like are eliminated by cutting. For this reason, the brake rotor-equipped wheel bearing device is restored to its cutting-completed state by assembling the processed brake-equipped wheel bearing device to an actual car. The surface runout of the pad slide surfaces during rotation of the brake rotor is very small, making it possible to rotate the brake rotor with high accuracy.
The conventional processing method for cutting the pad slide surfaces of the brake rotor of a brake rotor-equipped wheel bearing device put in a mounted state is a processing method intended to suppress the surface runout of the pad slide surfaces during rotation of the brake rotor, so as to prevent the occurrence of vibrations during braking. Of the outer and inner members relatively rotating through rolling elements, the outer member is fixed, and in this state the pad slide surfaces of the brake rotor assembled to the inner member are cut. The deformation of the rolling element contact surface during cutting load application causes the runout in the bearing rotation axis and the processing axis, resulting in the corresponding degradation of the surface runout accuracy. Referring to FIG. 9, the inner member 6 is rotated with the outer member 2 of a brake rotor-equipped wheel bearing device 1 being held by a chuck device 4, and the pad slide surfaces 8a and 8b of a brake rotor 8 are lathed with the reference surface defined by the flange surface 2a of the outer member 2. For this reason, the accuracies (axial runout, rigidity, etc.) of the bearing itself influence the processed brake rotor accuracy.